Targeting the membrane-proximal C2-set domain of CD33 for improved CAR T cell therapy.

Current CD33-targeted immunotherapies typically recognize the membrane-distal V-set domain of CD33. Here, we show that decreasing the distance between T cell and leukemia cell membrane increases the efficacy of CD33 chimeric antigen receptor (CAR) T cells. We therefore generated and optimized second-generation CAR constructs containing single-chain variable fragments from antibodies raised against the membrane-proximal C2-set domain, which bind CD33 regardless of whether the V-set domain is present (CD33PAN antibodies). CD33PAN CAR T cells resulted in efficient tumor clearance and improved survival of immunodeficient mice bearing human AML cell xenografts and, in an AML model with limited CD33 expression, forced escape of CD33neg leukemia. Compared to CD33V-set CAR T cells, CD33PAN CAR T cells showed greater in vitro and in vivo efficacy against several human AML cell lines with differing levels of CD33 without increased expression of exhaustion markers. CD33PAN moieties were detected at a higher frequency on human leukemic stem cells, and CD33PAN CAR T cells had greater in vitro efficacy against primary human AML cells. Together, our studies demonstrate improved efficacy with CAR T cells binding CD33 close to the cell membrane, providing the rationale to investigate CD33PAN CAR T cells further toward possible clinical application.

Allogeneic Hematopoietic Cell Transplantation for Acute Myeloid Leukemia in Adults over 70 years old.

The advent of reduced-intensity conditioning regimens, improvements in graft-versus-host disease prophylaxis, and better supportive care have permitted increasing use of allogeneic hematopoietic cell transplantation (allo-HCT) in adults age ≥70 with AML. However, while potentially curative, non-relapse mortality and relapse represent the main causes of treatment failure, highlighting the importance of refining both patient selection and transplant strategies. At the same time, continuously evolving non-transplant therapies and transplant technologies mandate prospective trials (re-)examining the role of allo-HCT and its optimal delivery.

Relationship between morphologic remission with or without hematologic recovery and outcome after allogeneic hematopoietic cell transplantation in adult acute myeloid leukemia.

Outcomes of adults with AML after allografting vary widely. While numerous covariates have been associated with relapse, non-relapse mortality (NRM), and/or shorter survival, the impact of incomplete blood count recovery before transplantation has remained unclear. To address this uncertainty, we examined all adults with AML or MDS/AML who received an allograft in first or second remission between 2006 and 2023 at a single institution. Of 1264 patients, 891 (70%) met criteria for CR, whereas 291 (23%), 24 (2%), and 58 (5%) were classified as CRh, CRi, and morphologic leukemia-free state (MLFS), respectively. CR, CRh, CRi, and MLFS patients differed significantly regarding demographics, disease biology, pre-transplant measurable residual disease, and types of transplants. After multivariable adjustment, outcomes for CRh and CRi patients were not significantly different from each other or from those of CR patients. In contrast, outcomes of MLFS patients were substantially worse than those of CR and CRh patients, with significantly higher risk of NRM and relapse, and significantly shorter relapse-free and overall survival. Similar results were obtained in several distinct subsets. Together, our analysis provides empiric evidence for the importance of distinguishing MLFS from CR and CRh patients for optimized risk assessment and, possibly, individualized treatment decision making.

Care Patterns and Barriers to Outpatient Care for Adults With AML Following Intensive Chemotherapy at NCCN Member Institutions.

BACKGROUND: Prolonged hospitalization following intensive (re)induction chemotherapy for acute myeloid leukemia (AML), while standard, is costly and resource intense, limits inpatient bed capacity, and negatively impacts quality of life. Early hospital discharge (EHD) following completion of chemotherapy has proven safe as an alternative at select institutions, but is not widely implemented. PATIENTS AND METHODS: From February 2023 through May 2023, the NCCN Best Practices Committee conducted a survey evaluating AML hospitalization patterns, care models, and barriers to EHD at its 33 member institutions. RESULTS: A total of 30 (91%) institutions completed the survey; two-thirds treat >100 patients with AML annually and 45% treat more than half of these with intensive chemotherapy. In the (re)induction setting, 80% of institutions keep patients hospitalized until blood count recovery, whereas 20% aim to discharge patients after completion of chemotherapy if medically stable and logistically feasible. The predominant reasons for the perceived need for ongoing hospitalization were high risk of infection, treatment toxicities, and lack of nearby/accessible housing. There was no significant association between ability to practice EHD and annual AML volume or treatment intensity patterns (P=.60 and P=.11, respectively). In contrast, in the postremission setting, 87% of centers support patients following chemotherapy in the outpatient setting unless toxicities arise requiring readmission. Survey responses showed that 80% of centers were interested in exploring EHD after (re)induction but noted significant barriers, including accessible housing (71%), transportation (50%), high toxicity/infection rate (50%), high transfusion burden (50%), and limited bed availability for rehospitalization (50%). CONCLUSIONS: Hospitalization and care patterns following intensive AML therapy vary widely across major US cancer institutions. Although only 20% of surveyed centers practice EHD following intensive (re)induction chemotherapy, 87% do so following postremission therapy. Given the interest in exploring the EHD approach given potential advantages of EHD for both patients and health care systems, strategies to address identified medical and logistical barriers should be explored.

Second Allogeneic Hematopoietic Cell Transplantation for Relapsed Adult Acute Myeloid Leukemia: Outcomes and Prognostic Factors.

Second allogeneic hematopoietic cell transplantation (HCT2) is potentially curative for adults with acute myeloid leukemia (AML) or myelodysplastic neoplasm (MDS)/AML experiencing relapse after a first allograft (HCT1), but prognostic factors for outcomes are poorly characterized. To provide a detailed analysis of HCT2 outcomes and associated prognostic factors in a large single-center cohort, with a focus on identifying predictors of relapse and nonrelapse mortality (NRM), we studied adults ≥18 years who underwent HCT2 at a single institution between April 2006 and June 2022 for relapsed AML (n = 73) or MDS/AML (n = 8). With a median follow-up among survivors of 74.0 (range: 10.4 to 187.3) months, there were 30 relapses and 57 deaths, of which 29 were NRM events, contributing to the estimates for relapse, overall survival (OS), relapse-free survival (RFS), and NRM. Three-year estimates for relapse, RFS, and OS were 37% (95% confidence interval: 27% to 48%), 32% (23% to 44%), and 35% (26% to 47%). The rate of NRM at 100 days and 18 months was 20% (12% to 29%) and 28% (19% to 39%). Outcomes differed markedly across patient subsets and were substantially worse for patients who underwent HCT2 with active disease (ie, morphologic evidence of bone marrow and/or extramedullary disease), for patients who relapsed ≤6 months after HCT1, and for patients with higher HCT-specific Comorbidity Index (HCT-CI) or treatment-related mortality (TRM) scores. After multivariable adjustment, active disease was associated with a higher risk of relapse (hazard ratio [HR] = 3.19, P = .006) and shorter RFS (HR = 2.41, P = .008) as well as OS (HR = 2.17, P = .027) compared to transplant in morphologic remission without multiparameter flow cytometric evidence of measurable residual disease. Similarly, a relapse-free interval ≤6 months after the first allograft was associated with higher risk of relapse (HR = 5.86, P < .001) and shorter RFS (HR = 2.86; P = .001) and OS (HR = 2.45, P = .003). Additionally, a high HCT-CI score was associated with increased NRM (HR = 4.30, P = .035), and shorter RFS (HR = 3.87, P = .003) and OS (HR = 3.74, P = .006). Likewise, higher TRM scores were associated with increased risk of relapse (HR = 2.27; P = .024) and NRM (HR = 2.01, P = .001), and inferior RFS (HR = 1.90 P = .001) and OS (HR = 1.88, P = .001). A significant subset of patients with AML or MDS/AML relapse after HCT1 are alive and leukemia-free 3 years after undergoing HCT2. Our study identifies active leukemia at the time of HCT2 and early relapse after HCT1 as major adverse prognostic factors, highlighting patient subsets in particular need of novel therapeutic approaches, and supports the use of the HCT-CI and TRM scores for outcome prognostication.

Safety and tolerability of AMG 330 in adults with relapsed/refractory AML: a phase 1a dose-escalation study.

AMG 330, a bispecific T-cell engager (BiTE®) that binds CD33 and CD3 on T cells facilitates T-cell-mediated cytotoxicity against CD33+ cells. This first-in-human, open-label, dose-escalation study evaluated the safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy of AMG 330 in adults with relapsed/refractory acute myeloid leukemia (R/R AML). Amongst 77 patients treated with AMG 330 (0.5 µg/day-1.6 mg/day) on 14-day or 28-day cycles, maximum tolerated dose was not reached; median duration of treatment was 29 days. The most frequent treatment-related adverse events were cytokine release syndrome (CRS; 78%) and rash (30%); 10% of patients experienced grade 3/4 CRS. CRS was mitigated with stepwise dosing of AMG 330, prophylactic dexamethasone, and early treatment with tocilizumab. Among 60 evaluable patients, eight achieved complete remission or morphologic leukemia-free state; of the 52 non-responders, 37% had ≥50% reduction in AML bone marrow blasts. AMG 330 is a promising CD33-targeted therapeutic strategy for R/R AML.

Intensive Reinduction Chemotherapy Followed by Early Allogeneic Hematopoietic Cell Transplantation for Relapsed/Refractory High-Grade Myeloid Neoplasms.

Outcomes for adults with relapsed/refractory (R/R) high-grade myeloid neoplasms remain poor, with allogeneic hematopoietic cell transplantation (HCT) the sole therapy likely to result in cure. We conducted the present study to determine the feasibility of early HCT-within 60 days of beginning reinduction chemotherapy-to see whether getting patients to HCT in an expeditious manner would expand the number of patients being offered this curative option. In this proof-of-principle feasibility study, we included adults age 18 to 75 years with R/R myeloid malignancies with ≥10% blood/marrow blasts at diagnosis who were eligible for a reduced-intensity HCT. Subjects received reinduction chemotherapy with cladribine, cytarabine, mitoxantrone, and filgrastim (CLAG-M) and proceeded to HCT with reduced-intensity conditioning (fludarabine/ melphalan). We enrolled 30 subjects, all of whom received CLAG-M reinduction, although only 9 underwent HCT within 60 days (<15, the predetermined threshold for feasibility "success"), with a median time to HCT of 48 days (range, 42 to 60 days). Eleven additional subjects received HCT beyond the target 60 days (off-study), with a median time to transplantation of 83 days (range, 53 to 367 days). Barriers to early HCT included infection, physician preference, lack of an HLA-matched donor, logistical delays, and disease progression, all of which may limit the real-world uptake of such early-to-transplantation protocols.

Dose-Adjusted EPOCH Plus Inotuzumab Ozogamicin in Adults With Relapsed or Refractory B-Cell ALL: A Phase 1 Dose-Escalation Trial.

Importance: Options for adults with relapsed or refractory B-cell acute lymphoblastic leukemia or lymphoma (B-ALL) are limited, and new approaches are needed. Inotuzumab ozogamicin (InO) has been combined with low-intensity chemotherapy, with modest improvements over historical controls, and dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (DA-EPOCH) treatment is safe and active for newly diagnosed ALL. Objective: To assess the safety and clinical activity of DA-EPOCH and InO in adults with relapsed or refractory B-ALL. Design, Setting, and Participants: This single-center, single-arm, nonrandomized, phase 1 dose-escalation trial included adults with relapsed or refractory CD22+ B-ALL and was conducted between September 2019 and November 2022. At least 5% blood or marrow blasts or measurable extramedullary disease (EMD) was required for enrollment. Interventions: DA-EPOCH was given on days 1 to 5, while InO was given on day 8 and day 15 of a 28-day cycle. Three dose levels were studied using a bayesian optimal interval design. Main Outcomes and Measures: The primary outcome was the maximum tolerated dose of InO when combined with DA-EPOCH, defined as the highest dose level that produced a rate of dose-limiting toxicity below 33%. Secondary objectives included response rates, survival estimates, and descriptions of toxic effects. Results: A total of 24 participants were screened and enrolled (median age, 46 [range, 28-76] years; 15 [62%] male). The median number of lines of prior therapy was 3 (range, 1-12). Three of 11 participants (27%) treated at the highest dose level (InO, 0.6 mg/m2, on day 8 and day 15) experienced dose-limiting toxicity, making this the maximum tolerated dose. No deaths occurred during the study, and only 1 patient (4%; 95% CI, 0.1%-21%) developed sinusoidal obstructive syndrome after poststudy allograft. The morphologic complete response rate was 84% (95% CI, 60%-97%), 88% (95% CI, 62%-98%) of which was measurable residual disease negative by flow cytometry. Five of 6 participants with EMD experienced treatment response. The overall response rate was 83% (95% CI, 63%-95%). Median overall survival, duration of response, and event-free survival were 17.0 (95% CI, 8.4-not reached), 15.0 (95% CI, 6.7-not reached), and 9.6 (95% CI, 4.5-not reached) months, respectively. Conclusions: In this study, adding InO to DA-EPOCH in adults with relapsed or refractory B-ALL was feasible, with high response rates and sinusoidal obstructive syndrome occurring rarely in a heavily pretreated population. Many patients were able to proceed to poststudy consolidative allogeneic hematopoietic cell transplant and/or chimeric antigen receptor T-cell therapy. Further investigation of this combination is warranted. Trial Registration: ClinicalTrials.gov Identifier: NCT03991884.

Preclinical Characterization of the Anti-Leukemia Activity of the CD33/CD16a/NKG2D Immune-Modulating TriNKET® CC-96191.

Increasing efforts are focusing on natural killer (NK) cell immunotherapies for AML. Here, we characterized CC-96191, a novel CD33/CD16a/NKG2D immune-modulating TriNKET®. CC-96191 simultaneously binds CD33, NKG2D, and CD16a, with NKG2D and CD16a co-engagement increasing the avidity for, and activation of, NK cells. CC-96191 was broadly active against human leukemia cells in a strictly CD33-dependent manner, with maximal efficacy requiring the co-engagement of CD16a and NKG2D. A frequent CD33 single nucleotide polymorphism, R69G, reduced CC-96191 potency but not maximal activity, likely because of reduced CD33 binding. Similarly, the potency, but not the maximal activity, of CC-96191 was reduced by high concentrations of soluble CD33; in contrast, the soluble form of the NKG2D ligand MICA did not impact activity. In the presence of CD33+ AML cells, CC-96191 activated NK cells but not T cells; while maximum anti-AML efficacy was similar, soluble cytokine levels were 10- to >100-fold lower than with a CD33/CD3 bispecific antibody. While CC-96191-mediated cytolysis was not affected by ABC transporter proteins, it was reduced by anti-apoptotic BCL-2 family proteins. Finally, in patient marrow specimens, CC-96191 eliminated AML cells but not normal monocytes, suggesting selectivity of TriNKET-induced cytotoxicity toward neoplastic cells. Together, these findings support the clinical exploration of CC-96191 as in NCT04789655.

CPX-351 Pharmacokinetics and Safety in Adults with Hematologic Malignancies and Renal Function Impairment: Phase 1 Trial.

This open-label phase 1 study (clinicaltrials.gov, NCT03555955) assessed CPX-351 pharmacokinetics (PK) and safety in patients with hematologic malignancies with normal or impaired renal function. Patients were enrolled into three cohorts based on their creatinine clearance (CrCl): ≥90 mL/min (Cohort 1, normal renal function, n = 7), 30 to <59 mL/min (Cohort 2, moderate renal impairment, n = 8), or <30 mL/min (Cohort 3, severe renal impairment, n = 6). Patients received intravenous CPX-351 for initial induction; blood and urine samples were collected for PK analysis. The primary objective was to assess the PK parameters for cytarabine, daunorubicin, and their respective metabolites, arabinosyluracil (Ara-U) and daunorubicinol. Renal impairment did not significantly impact the cytarabine, daunorubicin, or daunorubicinol exposure, but it caused a slight increase in the Ara-U exposure. The CPX-351 side effect profile was similar in patients with impaired renal function compared to those with normal renal function. All the patients reported ≥1 treatment-emergent adverse event (TEAE), most commonly febrile neutropenia and nausea (57% each) and hyperglycemia (43%); no patients discontinued treatment due to TEAEs. These data suggest that CPX-351 dose adjustment is not required for patients with hematologic malignancies with moderate or severe renal impairment.

Impact of socioeconomic disparities on outcomes in adults undergoing allogeneic hematopoietic cell transplantation for acute myeloid leukemia.

Racial and socioeconomic disparities impact outcomes after chemotherapy and limit access to allogeneic hematopoietic cell transplantation (HCT) in acute myeloid leukemia (AML), yet studies have yielded mixed results on the influence of disparities on post-HCT outcomes. Therefore, we studied 1024 adults with AML who underwent allogeneic HCT between 5/2006 and 10/2021 at a single large university-affiliated cancer center. Collected data included non-biologic and demographic characteristics (including race/ethnicity, marital status, distance traveled, and household size), transplant- and disease-related characteristics, and area-level and individual-level socioeconomic factors (i.e., area deprivation index and occupational status). After multivariable adjustment, no socioeconomic- or non-biologic factors were associated with non-relapse mortality (NRM), overall survival (OS), relapse-free survival (RFS), or relapse except being married (associated with improved NRM: hazard ratio [HR] = 0.7 [0.50-0.97]) and having no insurance (associated with worse OS: HR = 1.49 [1.05-2.12] and RFS: HR = 1.41 [1.00-1.98]). Despite a relatively racially homogenous cohort, Asian race was associated with improved NRM (HR = 0.47 [0.23-0.93]) and American Indian/Alaskan Native race was associated with higher relapse risk (HR = 2.45 [1.08-5.53]). In conclusion, in our retrospective analysis, socioeconomic-, demographic-, and non-biologic factors had limited impact on post-HCT outcomes in AML patients allografted in morphologic remission. Further research is needed to investigate disparities among HCT-eligible patients.

Relative prognostic value of flow cytometric measurable residual disease before allogeneic hematopoietic cell transplantation for adults with MDS/AML or AML.

Multiparameter flow cytometry (MFC) measurable residual disease (MRD) before allogeneic hematopoietic cell transplantation (HCT) independently predicts poor outcomes in acute myeloid leukemia (AML). Conversely, its prognostic value in the newly defined disease entity, myelodysplastic neoplasm (MDS)/AML is unknown. To assess the relationship between disease type, pre-HCT MRD, and post-HCT outcomes, we retrospectively analyzed 1265 adults with MDS/AML (n = 151) or AML (n = 1114) who received a first allograft in first or second morphologic remission at a single institution between April 2006 and March 2023. At 3 years, relapse rates (29% for MDS/AML vs. 29% for AML, p = .98), relapse-free survival (RFS; 50% vs. 55%, p = .22), overall survival (OS; 52% vs. 60%, p = .073), and non-relapse mortality (22% vs. 16%, p = .14) were not statistically significantly different. However, a significant interaction was found between pre-HCT MFC MRD and disease type (MDS/AML vs. AML) for relapse (p = .009), RFS (p = .011), and OS (p = .039). The interaction models indicated that the hazard ratios (HRs) for the association between pre-HCT MRD and post-HCT outcomes were lower in patients with MDS/AML (for relapse: HR = 1.75 [0.97-3.15] in MDS/AML vs. 4.13 [3.31-5.16] in AML; for RFS: HR = 1.58 [1.02-2.45] vs. 2.98 [2.48-3.58]; for OS: HR = 1.50 [0.96-2.35] vs. 2.52 [2.09-3.06]). On the other hand, residual cytogenetic abnormalities at the time of HCT were equally informative in MDS/AML as in AML patients. Our data indicate that MFC-based pre-HCT MRD testing, but not testing for residual cytogenetic abnormalities, is less informative for MDS/AML than AML patients when used for prognostication of post-HCT outcomes.

Crenolanib and Intensive Chemotherapy in Adults With Newly Diagnosed FLT3-Mutated AML.

PURPOSE: Crenolanib is a second-generation tyrosine kinase inhibitor with activity against FLT3-ITD- and TKD-mutant AML. We conducted a trial of crenolanib plus intensive chemotherapy in adults with newly diagnosed FLT3-mutant AML. METHODS: Eligible patients were 18 years and older. Induction chemotherapy consisted of cytarabine (100 mg/m2) continuous infusion on days 1-7 and anthracycline (daunorubicin 60-90 mg/m2 or idarubicin 12 mg/m2, once daily) on days 1-3 followed by consolidation with high-dose cytarabine (1-3 g/m2 twice daily on days 1, 3, 5) and/or allogeneic transplant. Crenolanib (100 mg thrice a day) was given from day 9 until 72 hours before the next cycle, after consolidation, and for 12 months after consolidation or transplant. RESULTS: Forty-four patients (median age, 57; range, 19-75 years) were enrolled. Thirty-six had FLT3-ITD, and 11 had FLT3-TKD mutations. European LeukemiaNet 2017 disease risk was favorable in 34%, intermediate in 30%, and adverse in 36%. The overall response rate was 86% (complete remission [CR], 77%; CR with incomplete count recovery [CRi], 9%): 90% in patients 60 years and younger and 80% in older patients. Measurable residual disease-negative CR/CRi rates were 89% and 45%, respectively. With a 45-month follow-up, median overall survival has not been reached and the median event-free survival was 44.7 months. Among younger patients, the estimated 3-year survival was 71.4% with 15% cumulative incidence of relapse. Treatment-related serious adverse events included febrile neutropenia, diarrhea, and nausea. The median time to platelets ≥100,000/µL and absolute neutrophil count ≥1,000/µL during induction was 29 and 32 days, respectively. No new FLT3-mutant clones were detected at relapse in patients completing consolidation. CONCLUSION: Crenolanib plus intensive chemotherapy in adults with newly diagnosed FLT3-mutant AML results in high rate of deep responses and long-term survival with acceptable toxicity. A randomized trial of crenolanib versus midostaurin plus chemotherapy in younger patients is ongoing.

Efficient long-term multilineage engraftment of CD33-edited hematopoietic stem/progenitor cells in nonhuman primates.

Current immunotherapeutic targets are often shared between neoplastic and normal hematopoietic stem and progenitor cells (HSPCs), leading to unwanted on-target, off-tumor toxicities. Deletion or modification of such targets to protect normal HSPCs is, therefore, of great interest. Although HSPC modifications commonly aim to mimic naturally occurring phenotypes, the long-term persistence and safety of gene-edited cells need to be evaluated. Here, we deleted the V-set domain of CD33, the immune-dominant domain targeted by most anti-CD33 antibodies used to treat CD33-positive malignancies, including acute myeloid leukemia, in the HSPCs of two rhesus macaques, performed autologous transplantation after myeloablative conditioning, and followed the animals for up to 3 years. CD33-edited HSPCs engrafted without any delay in recovery of neutrophils, the primary cell type expressing CD33. No impact on the blood composition, reconstitution of the bone marrow stem cell compartment, or myeloid differentiation potential was observed. Up to 20% long-term gene editing in HSPCs and blood cell lineages was seen with robust loss of CD33 detection on myeloid lineages. In conclusion, deletion of the V-set domain of CD33 on HSPCs, progenitors, and myeloid lineages did not show any adverse effects on their homing and engraftment potential or the differentiation and functionality of myeloid progenitors and lineages.

Hyper-CVAD versus dose-adjusted EPOCH as initial treatment for adults with acute lymphoblastic leukemia.

OBJECTIVES: We recently performed a single-arm phase II trial of DA-EPOCH in adults with acute lymphoblastic leukemia (ALL). We sought to compare these results to those with standard Hyper-CVAD. METHODS: We created a retrospective matched cohort of patients who received Hyper-CVAD (n = 69) at our center and otherwise met eligibility criteria for the DA-EPOCH trial (n = 53). RESULTS: Our outcomes support the use of Hyper-CVAD over DA-EPOCH in Ph- disease for both overall survival (OS; HR 0.18, p = .004) and event-free survival (EFS; HR 0.51, p = .06). In contrast, outcomes were similar in Ph+ disease (OS HR 0.97, p = .96; EFS HR 0.65, p = .21). Rates of morphologic remission and measurable residual-disease negativity were similar between the regimens. Hyper-CVAD was associated with significantly more febrile neutropenia (OR 1.9, p = .03) and a greater incidence of Grade 4 or 5 adverse events (20% vs. 6%). Average transfusions per cycle of both red blood cells (p < .001) and platelets (p < .001) were five-fold higher with Hyper-CVAD. CONCLUSIONS: Our findings support continued use of Hyper-CVAD for Ph- ALL but suggest that DA-EPOCH may be a reasonable alternative for Ph+ ALL. These data also highlight a potential role for DA-EPOCH in resource-limited settings or when more intense therapy is not feasible.